Overfilling main tank with LRA transfer pump
- Thread starter kcjaz
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bloc
SILVER Star
Nope.
Fuel supply and return lines run to the fuel pump/pickup/level module that isn’t installed in this tank. It drops into the round section that is taped off.
I realize this is a 200 series forum, but if you are interested in LRA products, and their effects on OEM LC fuel and evap systems, my thread on my customization of the LRA Aux 24 is quite a rabbit hole of its own. In 2004, Toyota changed the 100 series evap system, to essentially, be more finicky. So the weaknesses of the LRA system are most pronounced in the 2004-2007 LCs. I've customized my LRA Aux system to be completely valved off (electric ball valves) from the OEM fuel system, because I was getting dangerous boiling and over-pressurization in the summer, during elevation gain, and during bumpy elevation gains. Put all those together, with high ethanol (extra boily) Utah fuel, and it's a recipe for disaster. I am now finishing my customization to more or less turn the LRA Aux 24 into a marine-style spare tank, but that still uses the LRA dual-filler neck (customized) and their Aux 24 (customized). Enjoy, and you'll probably glean some tips to keep your 200 series systems running better. Be grateful they more or less work as designed in your 200s. Not the case for 100s, and certainly not for 04-07 100s. They won't even sell them to us anymore.
2006 LC w/ LRA Aux 24 - Fill, Venting, Fumes, Dripping & Over-Pressurization Issues
2006 LC w/ LRA Aux 24 - Fill, Venting, Fumes, Dripping & Over-Pressurization Issues
bloc
SILVER Star
These mods will prevent fuel boiling? Is hot fuel as much of an issue with stock 100-series as it is 200?
Unfortunately That method there will not work because the evap system-vent needs it's vent to the atmosphere so it can pressurize the tank/s. You have the evap vent going to the filler box which is capped and within the "closed system".
The evap system maintains a set pressure within the closed-system and it can ONLY do that by using it's vent to atmosphere.
Hope that makes sense.
The evap system maintains a set pressure within the closed-system and it can ONLY do that by using it's vent to atmosphere.
Hope that makes sense.
I do know of some anecdotal reports of fuel boiling in 100 series. Although I never had it prior to my LRA installation. I do still have a vent to atmosphere downline from that OEM canister. Think of it like this: when you add another 24 gal. of fuel to an OEM eval system (now approx. 50 gall), it effectively doubles the vaporization pressure, and doubles the work the canister has to do - and can foul the canister and cause issues with system equalization/pressurization. I have a buddy with a 200 who's been having this issue.
On the LRA dual-filler neck for the 100 series, LRA foolishly co-located the 3/8" infill port from the LRA tank, and the 1/4" vent breather from the OEM canister right next to each other in the cylindrical fill neck. Anytime I would pump fuel forward from the LRA to the OEM tank (via the fill neck), liquid fuel would wrap around the cylinder and dump down that vent breather into the canister. (Great design, mates - throw another shrimp on the barbie!) So when I separated them with my dual-filler neck mod, it completely eliminated that issue. I think the 200 LRA fill neck was better designed, from what I recall.
You can see those mods here: The Final Solution
Here's how my system works. The LRA tank is essentially designed like a marine tank, with with an electric valve that allow me to fill it with the LRA duel fill neck (modified), and pump forward with another valve - and that valve is tied into the LRA pump switch so that it automatically opens when I activate the pump. This allows the OEM system to pressurize as is need, and hasn't thrown any eval codes at me since I've been using it.
On the LRA dual-filler neck for the 100 series, LRA foolishly co-located the 3/8" infill port from the LRA tank, and the 1/4" vent breather from the OEM canister right next to each other in the cylindrical fill neck. Anytime I would pump fuel forward from the LRA to the OEM tank (via the fill neck), liquid fuel would wrap around the cylinder and dump down that vent breather into the canister. (Great design, mates - throw another shrimp on the barbie!) So when I separated them with my dual-filler neck mod, it completely eliminated that issue. I think the 200 LRA fill neck was better designed, from what I recall.
You can see those mods here: The Final Solution
Here's how my system works. The LRA tank is essentially designed like a marine tank, with with an electric valve that allow me to fill it with the LRA duel fill neck (modified), and pump forward with another valve - and that valve is tied into the LRA pump switch so that it automatically opens when I activate the pump. This allows the OEM system to pressurize as is need, and hasn't thrown any eval codes at me since I've been using it.
Last edited:
kcjaz
SILVER Star
- Thread starter
- #28
Very interesting. I need to think about this and digest more when I have some time. My initial thought is that there is merit in the idea that connecting the aux tank to the OEM evap system in a way that effectively exposes the OEM evap system to double the OEM volume of stored gasoline could cause problems. I know another 200 owner with the 24 LRA who, after a year or so started to get evap codes. He now only fill to the total 48 gal when he needs it for a road trip and now, so far so good. I need to check with him to see if he actually modified any of the plumbing.
Isolating the aux tank and venting it through its own charcoal filter does make sense to me if the increase in gas vapor is really overwhelming the OEM system.
What doesn't make sense to me is why high altitude boiling would be worse with an aux tank as thought the current theory with that was the hot fuel return recirculating back to the OEM tank. If the aux tanks boil, then it would seem to be the heat from the return fuel. If that was the case, wouldn't all vehicles boil their tanks at high altitude?
There are fuel coolers you can install to address some of it. Also, consider how close your exhaust is to the LRA tank. Some insulation between them can never hurt. I had fuel boiling in both OEM and LRA tanks. My system wasn't breathing because of the canister fouling, which effectively increases vapor entropy in the tanks, contributing to boiling. Sometimes, it's many things going on at once, which is why it can be hard to sort out.
bloc
SILVER Star
I’m not sure doubling the liquid volume doubles the vapor pressure. Doubling surface area (below boiling point) would double vapor volume.. when it starts boiling the math gets pretty complicated.
Do 100s with LRA boil only when it has fuel in the aux tank? Or will they do it when that tank is dry?
Do 100s with LRA boil only when it has fuel in the aux tank? Or will they do it when that tank is dry?
Is your friend running individual charcoal cannisters in his 200 series with the 24 gallon aux tank?
I'm not sure. Whatever LRA recommends.
I never experienced boiling in my 100 until I added the LRA tank. And yes, fuel surface area is this issue, not liquid fuel volume. So that means even with a 1/4 full LRA tank, you have the same surface area exposed as a full LRA tank, adding vapor to the OEM system. I've never checked for fuel boiling with an empty LRA tank specifically, which by the way is really never empty - you can't get all the fuel out, even by pumping past 'red blinking' mode a couple times.
